ALPR systems generally include various image processing and computer vision techniques for: (1) locating a license plate within a scene, (2) segmenting characters on the plate, and (3) performing optical character recognition to determine the character sequence.
One of the key steps in ALPR processing is identifying the issuing state of a license plate. Existing methods for estimating the issuing state from a captured plate image focus on identifying or measuring a number of key features on the plate, the presence or absence of logos, character spacing, character aspect ratio, color content in various locations on the plate, etc. The ability to accurately determine the issuing state for a license plate, however, continues to be a challenging aspect in the successful development and implementation of robust and efficient multi-state ALPR solutions.